Bump pymdown-extensions from 10.3.1 to 10.4 in /docs

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.3.1 to 10.4.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.3.1...10.4)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/requirements.txt

@@ -17,7 +17,7 @@ mkdocs-material==9.4.8
 mkdocs-material-extensions==1.3
 packaging==23.2
 Pygments==2.16.1
-pymdown-extensions==10.3.1
+pymdown-extensions==10.4
 pyparsing==3.1.1
 python-dateutil==2.8.2
 PyYAML==6.0.1